The Vascular Flora of Brown County, Nebraska

摘要

Brown County, located in north-central Nebraska contains several native vegetation types including sand hills mixed-grass prairie, gravelly mixed-grass prairie, ponderosa pine forests/savannas, sand hills-borders/mixed-grass prairie, upland deciduous forest, and wet lands. The Nebraska Sand Hills, which make up approximately 80% of Brown County, cover about 20,000 square miles of the state. This study reports a total of 726 plant species, subspecies, and varieties for Brown County, representing 105 families and 358 genera. Fourteen new county records were collected. A list of the vascular flora for Brown County is given and an index of similarity is used to compare Brown County to Banner, Dixon, Keith, and Seward Counties. The Niobrara River, which begins in Wyoming and flows 800 km east through Nebraska before it joins with the Missouri River, forms the northern border of Brown County. The river valley contains a rich flora, including many species that are unique within Nebraska. A possible explanation for the relatively high plant diversity of the area is that postglacial forests in the valley serve as a transition zone that supports species with both western and eastern affinities.